1. Field of the Invention
The present invention relates to a compact objective optical system having a long, thin shape and to an examination apparatus using the same, and more particularly, to an optical system that is inserted into an animal such as a mammal to perform in-vivo examination at high resolution and to an examination apparatus using the same.
This application is based on Japanese Patent Application No. 2005-041130, the content of which is incorporated herein by reference.
2. Description of Related Art
There are techniques in which a dye or fluorescent marker is attached to specific molecules, tissue, cells, and so on and fluorescence microscopes, confocal laser-scanning microscopes, and the like are used to examine the behavior of the molecules in the cells and tissue of living organisms.
The behavior of molecules in a live individual mammalian organism, such as a mouse, may differ from that in cultured cells. Therefore, examination of biological tissue and the interior of cells is carried out while the individual organism is alive (in-vivo).
When examining the interior of a living organism, because the outer diameter of the objective lens in conventional microscopes is large, it is necessary to make a large incision in the living organism to carry out examination. Making a large incision in a living organism, however, is highly invasive, and therefore long-term examination is impossible. An endoscope with a small diameter that is suitable for cellular examination with high magnification is proposed in Japanese Unexamined Patent Application Publication No. 2004-313772. Also, an objective optical system with a high numerical aperture, small outer diameter, and comparatively long overall length is disclosed in United States Patent Application No. 2004/0051957A1. With these objective optical systems, if a small hole is formed in the living organism and this optical system is inserted through the hole, it is possible to carry out examination of the living organism with minimal invasiveness.
However, because the overall optical-system length in the objective optical system disclosed in Japanese Unexamined Patent Application Publication No. 2004-313772 is small, it is difficult to insert the objective lens to the position of an internal organ that is deep inside the living organism. Also, this objective optical system suffers from the problem that the observation range is too small to examine changes at the tissue level.
Furthermore, the objective optical system disclosed in United States Patent Application No. 2004/0051957A1 does not sufficiently correct chromatic aberrations. Therefore, when carrying out white-light observation or fluorescence observation with this objective optical system, the wavelengths of excitation light and fluorescence produced in the specimen differ, which results in the problem of low resolution. This is a problem particularly when carrying out fluorescence observation using a confocal optical system, because the brightness of the fluorescence detected is low if the chromatic aberrations are not corrected.